The employee noticed dust was not collected sufficiently because dust adhered to around cutting machine more than usual. So, he removed the lid of the box for storing a circular saw and check the inside of it.
There are a lot of dusts in it and they jammed into the vent. He was trying to get rid of them.
He thought his hand did not touch the saw because a space in the box was about 10cm. He did not stop the rotation of the circular saw and got rid of dust. But his hand touched the saw and was injured.